Socioeconomic Status Alters Your Brain Structure

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1:02Smart, sharp, and slightly unhinged. Late night's fresh perspective. The last show with David Cooper. Inequality may not just live in your bank account, but also leave a fingerprint in your brain. What do I mean? Well, there's a study that suggests your social and economic status determines how your brain ages and how it starts to break down. Let's discuss all this with someone who's done research in this area. He's a research fellow in genetic epidemiology at the Bristol Medical School in the UK, and his name is Dr. David. Hill David, welcome to the show. Thank you David. Tell me a bit about yourself. Your research is so interesting before we jump in though. Yes, my work is looking at social economic status and how it may have causal effects on certain health outcomes, such as the aging of the brain. And in this piece of work what we've done is we've used genetic data to try and understand a modifiable, potentially modifiable, environmental exposures.

2:03So what we had to do was to try and get a very good measure of social economic status. So we took differences in income, differences in educational attainment, differences in individual's occupation, and differences in the social deprivation in the area in which they lived. And we performed something that's called a genome-wide association study. So what this does is look for individual differences in genetic variation, the co-vari with these differences in these four social economic status measures. And the reason we wanted to get a genetic measure of social economic status is so that we could perform a technique called Mendelian randomization. It sounds a bit like a sci-fi concept. Do you want to define that a little bit for me? Of course, of course. So Mendelian randomization is the idea of making a causal, is to be able to make a causal statement between two things. In this case, there's social economic status and aging of the brain. So in science, if you want to establish a causal relationship,

3:04you do something called a randomized control trial. You get two groups of participants equal in every way, and you give one of them the treatment of a fact, be it a certain kind of surgery and exercise program, a drug, and then because the groups are matched in every way, except for this treatment that you want to assess the impact of, the only difference is that treatment, and so you can say, because there's no differences, it must be the treatment that has this effect. Now, with social economic status or education, it's not possible to randomly allocate education to someone, nor is it possible to randomly allocate income to people or their occupation. But with Mendelian randomization, what you do is you take advantage of genetic variation with them population. You don't select your genotype. So if you have a genetic variant linked to, let's say, differences in income, you can then treat these genetic variants as randomly allocated in the participants in your group.

4:05So in this way, you've got a randomized control trial as a product of natural genetic inheritance. Got it. Okay, big picture. Are we saying that the paycheck of our parents, the where we grow up, can shape how our brain develops? Is that the basic premise here? What we seem to have found is that these differences in social economic status have a causal effect on something called white matter, hyperintensities. Now, what these are is very, very small lesions, sort of lesions in the brain. We don't really have them when we're children and young adults. As we age, we typically accumulate more and more across our lifespan. And these are predictive of cognitive decline and dementia in all the age. So individuals by the age of 40, if you have more of these white matter hyperintensities, you're more likely to develop dementia in all the age. Is the idea that the stress of having like not as much money or growing up with less socioeconomic status causes? These are, or I'm kind of missing the link here.

5:07How do these white matter hyperintensities develop in that environment? Well, at the moment, what we wanted to do is to establish if there is any causal link between these traits. We had a number of different brain ageing phenotypes. And by phenotypes, I just simply mean measures of the brain. So we had the white matter hyperintensities, as I mentioned, total brain volume, different volumetric measures for different sections of the brain. But nothing seemed to be a product or appears to be a product. Of differences in socioeconomic status, no cause of a relationship. There was a correlation, but not causal, not evidence of causality. So we don't know exactly which individual aspect of the environment is the causal element here. Only that we took our differences in education, income, occupation, and social deprivation. And we found then an effect of all four of these. But beyond this, what we did is we looked to see if a single underlying genetic dimension could explain the variation

6:09across these four socioeconomic status traits. Now, what I mean by this is that if you perform a genetic study on something like education attainment, you're not capturing the DNA consequences of getting a degree or not getting a degree. But rather, you're capturing other traits that lead to differences in how you get the degree. So your measure of education might be capturing your level of intelligence, your accountability, aspects of your personality, other aspects of yourself, how hard you work, how prone you are to disease. But we found there's this underlying genetic dimension across all four of these measures of socioeconomic status. And this underlying genetic dimension is what seemed to have the causal effect on brain health as measured by white matter type intensities in all the range. And you asked the question exactly how that link works. Yeah, could it be like stress access to healthcare access to healthier food? Like there's many such reasons, but I'm curious if you have any,

7:10I don't know, speculation as to which one it is. Or maybe it's the combination of them all. Well, by finding this underlying genetic dimension, what it indicates is that it wouldn't matter so much which of these aspects of socioeconomic status we sought to improve because we'd still be seeing the good effect on your brain health as engaged by white matter type intensities. That is to say, if you increase the amount of education in the population, you very well might be also having a protective effect against white matter type intensities, the same argument as if you increased or decreased, excuse me, social deprivation in the area. So we seemed to have found this broad idea of socioeconomic status having a causal effect. We did do in our study to see whether or not we're just capturing differences in cognitive ability. This is a very long history of cognitive ability being predictive of health, especially in older age. The research groups I've worked with in the PAMST include

8:11the Lodium-Birthga Houghton in Scotland, whereby they I chew test at every single 11-year-old in 1932 and 1947 in Scotland. And they found from that age 11 cognitive ability I chew test you can predict health in older age, be it aspects of dementia, how long people live, a prevalence of cardiovascular disease. So in our study, we had also used socioeconomic status without the effects of cognitive ability. And we still found that this socioeconomic status measure it seems to be having a protective effect against signs of dementia, wet matter type intensities, in older age. So at the moment, we can't quite pinpoint exactly what's in this sphere of effect, but we have good evidence that it is causal in some way. And our next stage of a mixed-stage with research is kind of picking this apart to determine where within this the effect is. So we kind of start nothing broad with finding something with a causal effect

9:11and then narrowing it down with this. Is there a major takeaway here like anything you would have society change so that as we age we'd have better brain health or more equitable society? That seems like an easy fix that we could do overnight. Yeah, I mean, there's a few things I'm keen to impress upon people from this world. The first of which is that yes, I use genetic data to understand socioeconomic status and you can use genetic data to predict socioeconomic status. But genetic in terms simply isn't a factor here. If you have a genetic variant that is indicative of a low level of education in the future, this doesn't mean it's destined. You've simply changed the environment, different schools, different areas, different everything. Nothing you set in stone with us. It's just described how things are currently in the samples that we looked at. Well, David, thanks so much for joining me. I appreciate you sharing your research. It is an interesting, fascinating link. And I appreciate you coming on the show. Thank you so much for having me. Dr. David Hill is a research fellow

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